Ansible request for CentOS6_Cent7SSL role to follow best practises

- [ ] Missing install
- [x] Bug in ansible playbook
- [ ] Request for new playbook addition

Details:
With the VPC bug on C6 fixed with #2372, I noticed that the role isn't really [idempotent](https://docs.ansible.com/ansible/latest/reference_appendices/glossary.html#term-Idempotency) as, if it fails halfway through, it can cause earlier tasks to fail. Certainly the `rpm` command I used in #2372 will fail if it tries to install the `openssl` packages when they've been installed before. Currently the role serves it's purpose, but I'd like to clear it up a bit (assuming I can and it doesn't NEED the hacks, because CentOS6 - which it may do).